This invention relates to an air inlet arrangement for the engine of a vehicle. The invention has been conceived in connection with the engine of an agricultural tractor and will, in the main, be discussed in relation thereto. However, it is to be noted that the invention is applicable to any vehicle.
It is commonplace to take ambient air, clean it and pass it to the air inlet manifold of an engine where it is used for mixing with the fuel in proportions to give the right air/fuel mixture for combustion. There are two main requirements in respect of the air fed to an engine, namely that it be free from foreign matter, such as dust, and be as cool as possible. The first requirement is met by providing an air cleaner or filter and this is conventional. Ideally, the air filter is mounted closely adjacent the engine so that there is only a relatively short air duct between the outlet of the air filter and the air inlet of the engine. This means that, if ambient air is to be taken in directly at the air filter, then an air intake has to be positioned in the vicinity of the air filter and, in the case of an agricultural tractor for example, this would mean providing an air intake pipe extending through the hood or cover for the engine compartment at a location immediately in front of the cab windscreen and thus this would interfere with the operator's visibility.
Accordingly, it has been the practice to move this air intake pipe to the front of the engine compartment so as to reduce inference with the operator's visibility but this has meant providing an air duct between the air inlet pipe and the air filter. This duct, which may be in the form of a hose of the order of 10 cm in diameter, is routed through the engine compartment to the air filter and this gives rise to two disadvantages. The first disadvantage is that the duct passes through the engine compartment, the temperature of which, in use of the vehicle, is considerably higher than the ambient temperature which means that the temperature of the air fed to the engine is elevated, thus detracting from the performance of the engine inasmuch as the higher the temperature of the air is, the less efficient the operation of the engine is. The second disadvantage is that the air duct obscures many components in the engine compartment, whereby access to these components for maintenance purposes is difficult. Furthermore, the air inlet pipe is normally fitted with a rain cowl or cap and both this cap and the pipe may have to be dismantled in order to gain access to the engine compartment.